Saturday, March 20, 2010

The Temperature Isn't The Only Thing Rising...

So is the range of the MINI-E. Now that (hopefully) the cold weather is behind us, so is the punishing effects the cold temperatures and the heater use has on the range of our cars. Today I drove 91 miles and still had an estimated range of 35 miles left to go. It was a leisurely drive at speeds around 40 mph, the kind of driving the MINI-E loves most so I expected to have good results, but a total range of 126 miles? I haven't seen my range that good since last September.

I was happy to read that the BMW ActiveE, the successor to the MINI-E will have a thermal management system that will warm or cool the battery pack to keep it at optimum operating efficiency. This is a feature that is dearly missed on the MINI-E and some of the other pioneers have been very critical of the car because of this omission. The reduced range in the winter months has caused some of the MINI-E drivers to lose faith in the car and not drive as much as they would like to. There are others, myself included who just adjusted their driving to accommodate the 20 or 30 less miles per charge that the car was getting. Then there were others like Jim McLaughlin (MINI-E # 458) who use a automobile cabin heater to pre-heat the cabin and thus the batteries. Jim has continued to record single-charge range well over 100 miles  for the entire winter, even when the temperature was down under 20 degrees. To me this is good news because it proves that a sophisticated thermal management system will allow the car to travel roughly the same distance regardless of the outside temperature.

8 comments:

  1. Can you leave the cars heater on to preheat it & warm up the batteries while it's charging?

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  2. No you cannot Earl. The heater will not work unless the car is turned on and the car cannot be turned on while it's charging. This car was put together quickly by BMW and little things like this were overlooked. That's what we're her for to find out things like this that make a big difference in the driving experience and usefulness of the car. BMW's next EV, the ActiveE will be able to heat or cool while charging, and you will be able to turn it on or off remotely from your smartphone.

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  3. Sounds like the unreliable aspect of the range will me a big problem for many people. You don't have to want to check the weather report to see if you can make an appointment the next day.

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  4. Anonymous: The MINI-E is a prototype vehicle and is not going to go into production. I would be disappointed if any major auto manufacturer sold an EV that was this susceptible to the ambient temperature. Yes, it would be a problem, but EV's that are going to be available for the general public will be engineered to cope with temperature variations better than the MINI-E does. I don't think it will be a big problem at all.

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  5. So the hotter the better?

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  6. No, definitely not! The batteries seem to perform the best when they are between 75 degrees and 98 degrees. Too hot is not good for the life of the batteries. This is why many EV's like Tesla have an active thermal management system to keep the battery temperature in the optimal range. This increases the driving range and the life of the batteries

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  7. The biggest reducer of range in the winter was running the cabin heater. While preheating will help I think they need a more efficient heater, and cabin temperature management, along with battery temperature management.

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  8. Robert, yes it is a huge draw. I did some testing a few times and drove without using the heater in the very cold. It wasn't very scientific but what I found is the heater use was responsible for about 50% of the range loss in the very cold weather. The other 50% was just that the batteries cannot efficiently disburse the stored energy when the modules get below 50 degrees. It's amazing how our full range came right back as soon as the temperatures got about 50.

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